Hodgkin's Disease is a human lymphoma, the etiology of which is still not well understood. The neoplastic cells of Hodgkin's Disease are known as Hodgkin and Reed-Sternberg (H-RS) cells. CD30 is a 120 kd surface antigen widely used as a clinical marker for Hodgkin's lymphoma and related hematologic malignancies (Froese et al., J. Immunol. 139:2081 (1987); Pfreundschuh et al., Onkologie 12:30 (1989); Carde et al., Eur. J. Cancer 26:474 (1990)). Originally identified by the monoclonal antibody Ki-1, which is reactive with H-RS cells (Schwab et al., Nature (London) 299:65 (1982)), CD30 was subsequently shown to be expressed on a subset of non-Hodgkin's lymphomas (NHL), including Burkitt's lymphoma, as well as several virally-transformed lines (human T-Cell Lymphotrophic Virus I or II transformed T-cells, and Epstein-Barr Virus transformed B-cells (Stein et al., Blood 66:848 (1985); Andreesen et al., Blood 63:1299 (1984)). That CD30 plays a role in normal lymphoid interactions is suggested by its histological detection on a small population of lymphoid cells in reactive lymph nodes, and by induced expression on purified T- and B-cells following lectin activation (Stein et al., Int. J. Cancer 30:445 (1982) and Stein et al., 1985, supra).
CD30 expression has also been detected on various non-Hodgkin's lymphomas (NHL), such as large-cell anaplastic lymphomas (LCAL), cutaneous T-cell lymphomas, nodular small cleaved-cell lymphomas, lymphocytic lymphomas, peripheral T-cell lymphomas, Lennen's lymphomas, immunoblastic lymphomas, T-cell leukemia/lymphomas (ATLL), adult T-cell leukemia (T-ALL), and centroblastic/centrocytic (cb/cc) follicular lymphomas (Stein et al., Blood 66:848 (1985); Miettinen, Arch. Pathol. Lab. Med. 116:1197 (1992); Piris et al., Histopathology 17:211 (1990); Burns et al., Am. J. Clin. Pathol. 93:327 (1990); Piris et al., Histopathology 18:25 (1991); Eckert et al., Am. J. Dermatopathol. 11:345 (1989); Gianotti et al., Am. J. Dermatopathol. 13:503 (1991); Maeda et al., Br. J. Dermatol. 121:603 (1989)). The association of the CD30 antigen with lymphoid malignancies has proven to be a useful marker for the identification of malignant cells within lymphold tissues, particularly lymph nodes. However, expression of CD30 has also been reported on a portion of embryonal carcinomas, nonembryonal carcinomas, malignant melanomas, mesenchymal tumors, and myeloid cell lines and macrophages at late stages of differentiation (Schwarting et al., Blood 74:1678 (1989); Pallesen et al., Am J. Pathol. 133:446 (1988); Mechtersheimer et al., Cancer 66:1732 (1990); Andreesen et al., Am. J. Pathol. 134:187 (1989)).
Cloning and expression of a gene encoding CD30 has been reported and CD30 has been characterized as a transmembrane protein that possesses substantial homology to the nerve growth factor receptor superfamily (Durkop et al., Cell 68:421, 1992). Durkop et al. suggest that CD30 is the receptor for one or more as yet unidentified growth factors, and recognize the importance of investigating the existence and nature of such growth factors in order to achieve insight into the etiology of Hodgkin's Disease.
Prior to the present invention, however, no such growth factors or other molecules that bind to the CD30 receptor were known. A need thus remained for identification and characterization of a ligand for CD30.